Mulch Calculator
Work out how much mulch a bed needs from its area and depth — in cubic yards, cubic feet, and standard 2 cu ft bags.
The mulch formula
Cubic yards = cubic feet ÷ 27 · Bags = cubic feet ÷ bag size
A 20 × 5 ft bed at 3 inches: 100 sq ft × 0.25 ft = 25 cu ft = 0.93 cubic yards ≈ 13 bags of 2 cu ft.
Depth, coverage, and buying in bulk
Aim for 2–3 inches of mulch — deep enough to block weeds and hold moisture, shallow enough not to suffocate roots. Keep it pulled back a few inches from stems and trunks to avoid rot ("volcano mulching" around trees is harmful). Bags are convenient for small beds, but the math turns quickly: one cubic yard is about 13.5 bags, and bulk delivery by the yard usually costs far less for anything sizeable. Measure irregular beds by splitting them into rectangles (see the square footage calculator). Mulch uses the same cubic-yard math as the concrete calculator.
Frequently asked questions
How much mulch do I need?
Area × depth (in feet) ÷ 27 for cubic yards. 100 sq ft at 3 inches ≈ 0.93 cu yd (13 bags).
How deep should mulch be?
2–3 inches; keep it away from stems and trunks.
How many bags in a cubic yard?
~13.5 bags of 2 cu ft. Bulk is cheaper for large areas.
Related calculators
Note: Estimates only; settling and uneven beds affect real coverage. Last reviewed: July 2026.